Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1999-03-24
2002-04-30
Lee, Cheukfan (Department: 2722)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S486000, C358S497000
Reexamination Certificate
active
06381043
ABSTRACT:
FIELD OF THE INVENTION
Background of the Invention
Nowadays, an image scanner has gradually become a standard peripheral equipment of a personal computer. Therefore, scanner manufacturers have been trying their best to improve the scanning quality, for example, to compensate brightness, chrominance, etc., and/or correct scanning line errors. On the other hand, high scanning speed is also a criterion of an exquisite image scanner.
In order to enhance the scanning speed of an image scanner, several devices and methods have been proposed in prior art. For example, please refer to
FIG. 1
which schematically shows home-sensor means for speeding up the movement of an image pickup module
11
from a standby line N to a scan start line M, i.e. a document reference line. In this case, it is assumed that the image pickup module
11
reaches the scan start line M after moving a distance D from the standby line N along the arrow direction. In other words, the image pickup module
11
directly moves a pre-determined distance, rather than moves pixel by pixel to detect the presence of a document, and then starts scanning. Therefore, the movement of the image pickup module
11
from the standby line N to the scan start line M is fast.
However, there likely to be defects resulting from errors of various parts and/or assembling inaccuracy in this home sensor means. For example, if the image pickup module
11
is inaccurately installed at a position lower than a predetermined one while assembling, i.e. the standby line is lowered, the actual scan start line M
1
will be accordingly lower than the document reference line M after the same distance D of movement, referring to the dotted lines and the dotted arrow in FIG.
1
. Therefore, the top portion
13
of the document
12
will be missed out in the scanning operation.
Another conventional means is proposed to avoid the missing of document data. Please refer to
FIG. 2
which schematically shows means for precisely determining a scan start point in an image scanner. On the scanning platform of this image scanner, a black region
21
is provided in front of a scan start line R where a front edge of a document
22
to be scanned is positioned. In this case, the image pickup module (not shown) quickly moves toward the black region
21
, and then slowly passes through the black region
21
after reaches the black region
21
to detect the disappearance of the black color. When the detected black color disappears, the image pickup module keeps on moving and begins to measure a distance Q along the arrow direction. It is assumed that the scan start line R is reached after the image pickup module moves the distance Q from the reference point P. By this way, the downshift error resulting from the downshift installation of the image pickup module, as shown in
FIG. 1
, can be avoided because the predetermined distance Q is measured from the lower edge of the black region, i.e. the reference point P, rather than from the standby line of the image pickup module. Nevertheless, there still exists a defect in this means. Generally, when the image pickup module reaches the scan start line R, the nth pixel unit of a CCD of the image pickup module is predetermined to serve as the start point of the same scanning line, and the nth pixel unit and the pixel units thereafter are used to simultaneously pick up the image of the document line by line. If the image pickup module slightly deflects from its pre-determined path owing to an assembling defect, the same distance Q of movement will make the image pickup module reach another deflective line rather than the pre-determined scan start line R so that the nth pixel unit of the CCD will be a little shifted, and the scanning of a left portion of the document might be missed out. In addition, the scanning lines will slant.
In the parent application bearing Ser. No. 09/152,152 and filed on Sep. 11, 1998, means for determining a scan start point quickly and precisely, and simultaneously realizing a deflection rate and/or an amplification error of the scan lines so as to enhance the overall scanning speed and improve the scanning quality of an image scanner is disclosed. Referring to
FIG. 3
which schematically show the operation of a preferred embodiment of the parent application, the above purpose can be achieved by providing on the platform
30
of the image scanner two pattern marks
322
and
323
between the home position H and the scan start S. The geometric shape of the pattern marks
322
and
323
are so specific that the coordinate of each of the points constituting the pattern marks can be calculated under certain known conditions. For example, it can be designed that the linking the points A, C and D constitutes an isosceles and right-angled triangle, i.e. ∠CAD=45°, ∠ADC=45° and ∠ACD=90°, and the linking of the points B, E and F constitutes another isosceles and right-angled triangle, i.e. ∠EBF=45°, ∠BFE=45° and ∠BEF=90°, so that the coordinate of each of the points constituting the pattern marks
322
and
323
can be calculated under certain known conditions through triangular functions.
When a scanning operation starts, the CCD
311
of the image scanner moves a pre-determined distance L
0
from the home position H quickly to reach a pre-scan position I, and reads coordinates of four reference points J, K, U and V of the pattern marks
322
and
323
at the pre-scan position I. According to the coordinates of the two reference points J and K, a further moving distance L
1
of the CCD
311
from the pre-scan position I to respective ultimate point A of the pattern mark
322
can be easily determined through a mathematical function, so the movement of the CCD in this stage can also be fast. Afterwards, the CCD
311
further quickly moves another pre-determined distance L
2
from the ultimate point A to the scan start S, and then starts scanning. Accordingly, the scanning speed would be satisfactory. Furthermore, it can be understood that the distance L
1
can be automatically adjusted to reach the same ultimate point A no matter if the CCD
311
starts moving accurately from the home position. Therefore, the determination of the scan start point would be relatively precise.
On the other hand, according to the coordinates of the reference points J and K, the coordinate of the point A can be calculated, and according to the coordinates of the reference points U and V, the coordinate of the point B can also be realized. Further, according to the coordinates of the points A and B, the deflection rate of the scan line can be calculated. Moreover, according to the coordinates of the points A and B and the measured distance L
3
between the points A and B, the amplification error of the scan line can also be realized. The deflection rate and the amplification error can be used to correct the scanning result so as to obtain a better scanning quality.
Although the image scanner of the parent application has been significantly improved in the precision and the speed of the determination of the scan start point and the scanning quality of the scan lines, the above means may suffer from the contamination spots on the platform. Generally, with reference to
FIG. 3
, the pattern marks
322
and
323
are printed on a white background region
324
with standard black. If the region
324
is contaminated and has spot(s) thereon, especially at the pre-scan position I, during the manufacturing process of the image scanner or after the scanner has been used for a period of time, the CCD
311
may erroneously reads the coordinates of the contamination spots instead of the reference points J, K, U and V so that an error in the determination of the distance L
1
and the coordinates of the points A and B in relation to the read coordinates may occur.
On the other hand, although the scanning speed of the image scanner of the parent application is satisfactory, there is still a demand for higher scanning speed.
SUMMARY OF THE INVENTION
Therefore, an object of th
Chen Bill
Tsai Jenn-Tsair
Lee Cheukfan
Mustek Systems Inc.
Skjerven Morrill & MacPherson LLP
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